This application claims priority to U.S. Provisional Patent No. 60/630,975, filed Nov. 24, 2004, incorporated herein by reference in its entirety. This invention was made with U.S. Government support under U.S. Army Medical Command, as part of the project “Detection and Remediation of Chemical Threat Agents” (TEES 32536/5975Q). The government has certain rights in this invention. Without limiting the scope of the invention, its background is described in connection with bacterial detection.
Bacteriophages are viruses that kill bacteria. Most bacteriophages have defined host-specificity, a characteristic that has led to the widespread use of bacteriophages for typing of pathogenic bacteria (“phage typing”; see, 1–3, 6, 8, 11, 12). Double-stranded DNA phages can be grouped into three main morphotypes: myophages, which have contractile tails; siphophages; which have flexible, non-contractile tails, and podophages, which have short, “stumpy” tails.
Bacteriophages are the most numerous biological entities, estimated at 1031 in the biosphere, and are unimaginably diverse. Phages exist with a wide range of host specificities, from narrow host range phages like λ, which infects only some strains of E. coli, to generalists like P1, which can inject its DNA into all enterobacteria and even myxobacteria. Consequently, phages have long been used as a “low-tech” method to type bacteria in clinical microbiology environments. Attempts to exploit the specificity of phages in detection and identification of pathogenic bacteria have been burdened by the requirement of culturing the target bacteria, growing the infected culture, and assaying the production of progeny virions, processes which at minimum require hours and also knowledge of the culture conditions is required.
The committed step in bacteriophage infection is irreversible adsorption. For double-stranded DNA (dsDNA) phages, the results from interactions between the specific adsorption apparatus, usually tail fibers, with specific receptors on the surface of the host cell. For two of the three main morphotypes of dsDNA phages, the myophages with contractile tails and the siphophages with flexible tails, the injection of DNA into the host cell follows rapidly and involves the transitory formation of a channel through which the phage DNA passes into the target cytoplasm. Concomitant with injection is a short-lived membrane depolarization and an efflux of K+ ions from the cytoplasm, at a rate of ˜106/sec per infected cell, before a poorly-understood re-sealing process occurs, allowing re-energization of the membrane and the commencement of the infection program.